The world's 7 billionth person will be born into a population more aware than ever of the challenges of sustaining life on a crowded planet but no closer to a consensus about what to do about it.
To some demographers the milestone foreshadows turbulent times ahead: nations grappling with rapid urbanization, environmental degradation and skyrocketing demand for healthcare, education, resources and jobs.
To others, a shrinking population, not overpopulation, could be the longer-term challenge as fertility rates drop and a shrinking workforce is pushed to support social safety for an aging populace.
"There are parts of the world where the population is shrinking and in those parts of the world, they are worried about productivity, about being able to maintain a critical mass of people," Babatunde Osotimehin, executive director of the U.N. Population Fund, told Reuters.
"Then there are parts of the world where the population is growing rapidly. Many of these countries face challenges in terms of migration, poverty, food security, water management and climate change and we need to call attention to it."
The United Nations says the world's seven billionth baby will be born on October 31.
No-one knows what circumstances the baby will be born into, but India's Uttar Pradesh -- a sugarcane-producing state with a population that combines that of Britain, France and Germany, in a country expected to overtake China as the world's most populous by 2030 -- provides a snapshot of the challenges it could face.
Pinky Pawar, 25, is due to give birth in Uttar Pradesh at the end of the month and is hoping her firstborn will not join the estimated 3 billion people living on less than $2 a day, with little hope of an education or a job.
"I want my child to be successful in life, so I must do my best to make this possible," she said, her hands over her swollen belly as she sat outside her mud and brick home in Sunhaida village.
In Sunhaida, poverty, illiteracy and social prejudice mark a life dominated by the struggle for survival that mirrors millions of others across the world.
With the number of people on earth more than doubling over the last half-century, resources are under more strain than ever before.
First among the short-term worries is how to provide basic necessities for the additional 2-3 billion people expected to be added in the next 50 years.
Water usage is set to increase by 50 percent between 2007 and 2025 in developing nations and 18 percent in developed ones, with much of the increased use in the poorest countries as rising rural populations move to towns and cities.
"The problem is that 97.5 percent of it (water) is salty and ... of the 2.5 percent that's fresh, two-thirds of that is frozen," says Rob Renner, executive director of the Colorado-based Water Research Foundation.
"So there's not a lot of fresh water to deal with in the world."
Nutritious food is in short supply in many parts of the globe. The World Bank says 925 million people are hungry today, partly due to rising food prices since 1995, a succession of economic crises and the lack of access to modern farming techniques and products for poor farmers.
To feed the two billion more mouths predicted by 2050, food production will have to increase by 70 percent, the U.N.'s Food and Agriculture Organization says.
But just as research, development and expansion of agricultural programs are critical, the public dollars pledged to this effort remain a pittance of what is needed, and are in fact in danger of sharp decline, experts say.